Proteoglycans are heterogeneous chemical compounds and they are responsible for the hydration of connective tissues. It is the intention of this proposal to isolate proteoglycan fractions from tissues such as skin, cornea, aorta. The isolated fractions containing single macromolecular species will be characterized regarding the macromolecular components: protein content, hyaluronic acid, dermatan sulfate, chondroitin 4 and 6 sulfate, keratan sulfate content will be determined whichever is present in the different fractions. The hydration properties of each proteoglycans will be studied by high vacuum vapor sorption studies. The macromolecular components that seem to influence most the hydration of the tissues will be studied as a function of ageing.